I have a freshly rebuilt engine that I just put in my 8. It was very hard to start at first but I started it and it revs glass smooth. (I didn't rev it past 5k) After holding the gas for 15 min I let it idle. It was ok, but definitely wasnt correct. (but it would stay running) I let it do this for 30 min, temp needle not even hitting the middle of the gauge, oil pressure a little past the middle of the gauge, and only a radiator light. (I had plenty of antifreeze.) I cut the car off, to go get something to eat. Went back to start it, had a hard time starting, but it got to running. Again, revving smooth as glass but now I had a CEL and it would idle a lot rougher than before. (The CEL code was P0171 System too lean.) I also noticed that I had a vacuum hose leaking. Right on top of the black part of the throttle body, the little piece it slides on to snapped off. So my questions are, is this normal for a fresh rebuild to behave like this before driving it? Also, is that vacuum hose the culprit for my CEL? (If not what is the most likely cause) And also just any other pointers would be greatly appreciated.

 

Also ive got all new good components in my ignition system.

 

Please try and keep all the posts about this in the same thread. ......

 

Ok do I need to delete or move it? Or just leave it here and use your advice for future posts?

 

I'll fix it....just do it going forward

 

But anyway, is there any advice for my issue? Will running the car lean hurt the motor?

 

A vacuum leak will most definitely cause rough idle and can cause the lean code. Fix that before doing anything else. And, yes, running lean can damage the engine.

 

Ok I'll fix that and come back with my results. Once the leak is fixed, do I need to do the press the brake 20 times procedure to see if the CEL goes away? Or if I fixed it It will go away without me clearing it.

 

Right, I did that before the first start. But do I need to do it again once I fix the vacuum leak?

 

^ Wont hurt, your symptoms definitely sound like a vacuum leak though, can you take a picture of the broken hose? Not sure if you mean it's on the Throttle body or the UIM, I'm thinking UIM though as the throttle body only has coolant lines going to it... which would mean on the UIM and a definite vacuum leak

 

Issue fixed, it was a combination of that vacuum line being off and the MAF being dirty. Idles perfectly now and starts a lot quicker.

 

Im also aware that the gauge on the dash is a "dummy" While idling in 90 degree weather it never even hits the middle. Just to be sure i infrared temp gunned the engine and my readings were this. (I was reeving a little too so its not full idle temps.

Exhaust side of the engine right by the manifold- 323 F

Spark plug side of the engine- 170 F

Top of the engine bay (pointed at alternator area)- 140 F